Figure 2.

The effect of ¹⁷O-labeled H₂O₂ on DMPO/^⋅OH formation. Incubation mixtures contained H₂O₂ (5 mM), DMPO (50 mM), and DTPA (100 μM) in a bicarbonate/CO₂ buffer. The reaction was initiated with either Fe(II)-EDTA (100 μM) or 100 μg of SOD or SOD mutants (G93A and A4V) as shown. Line positions from ¹⁷O and ¹⁶O couplings are shown by • and ○, respectively. The dotted lines show computer simulations of ESR spectra using the parameters a^N = 15.0 G and a^H = 15.0 G for DMPO/^⋅16OH and a^N = 15.0 G, a^H = 15.0 G, and a^17O = 4.6 G for DMPO/^⋅17OH.